Antimalarial heterocyclic compounds and a process for the preparation thereof

ABSTRACT

The present invention relates to an antimalarial heterocyclic compound of formula I, dimers thereof and process for the preparation thereof. Further, the present invention relates to a pharmaceutical composition of heterocyclic compound of formula I, dimers thereof for treating malarial infection.

FIELD OF THE INVENTION

The present invention relates to an antimalarial heterocyclic compound of formula I, dimers or a pharmaceutically acceptable salt thereof. Particularly, present invention relates to a process for the preparation of antimalarial heterocyclic compound of formula I, dimers or a pharmaceutically acceptable salt thereof. More particularly, the present invention relates to a pharmaceutical composition comprising heterocyclic compound of formula I, dimers or pharmaceutically acceptable salt thereof for treating or preventing malarial infection in a subject in need thereof comprises of administering a therapeutically effective amount of a compound formula I, dimers or pharmaceutically acceptable salt thereof.

BACKGROUND AND PRIOR ART OF THE INVENTION

Malaria a life threatening disease caused by bite of infected female anopheles mosquito. According to World health Organization (WHO) reports there are about 400 000 deaths caused globally by malaria. Malaria mainly caused by four species of protozoan i.e. Plasmodium falciparum, P. Vivax, P. Ovale, P. Malariae. Alkaloids are highly important pharmacophores and currently available methods for the synthesis of substituted pyridine based alkaloids are tedious, lengthy and low yielding. The natural products Marinoquinoline A-F, Aplidiopsamine A and related natural products have very good antimalarial activity. Marinoquinoline A isolated from the gliding bacterium Ohtaekwangia Kribbensis with Marinoquinoline B-F by Muller et al. in Journal of Natural product, 2011, 74, 603-608. Author mentioned that pyrroloquinoline shows weak antibacterial and antifungal activities. Whereas, Marinoquinoline A-F showed activity against Plasmodium falciparum K1 with IC₅₀ values ranging between 1.7 and 15 μM.

U.S. Pat. No. 9,518,051B2 assigned to Council Scientific & Industrial Research (CSIR) and granted on 13^(th) Dec 2016 discloses novel compounds with potential anti-malarial activity and process of synthesis thereof. Further, the process for the synthesis of known antimalarial natural products marinoquinazolinone A-F, aplidiopsamine A and their potential antimalarial analogues is disclosed.

The article titled ‘Pd-Catalyzed Imine Cyclization: Synthesis of Antimalarial Natural Products Aplidiopsamine A, Marinoquinoline A, and Their Potential Hybrid NCLite-M1’ by Santosh B. Mhaske* et. al published in the journal “ORGANIC LETTERS 2012 Vol. 14, No. 22 5804-5807” reports synthesis of antimalarial natural products. The article also reports new potential natural product hybrid NCLite-M 1.

To date, drug resistance observed in only two species i.e. Plasmodium falciparum, P. Vivax. Report also states that there is alarming rates of failure of dihydroartemisinin-piperaquine drug. Development of multi drug resistance strains of malaria parasite is great concern in controlling malaria worldwide. Transnational spreading of multidrug resistant is serious issue, hence there is need to find out novel antimalarial agent to combat the situation. In particular, there is urgent need to find out more effective drug to treat malaria as multi-drug resistance increasing worldwide. Accordingly, the present invention provides an antimalarial heterocyclic compounds of formula I or pharmaceutically acceptable salts thereof.

OBJECTS OF THE INVENTION

The main objective of the present invention is to provide an antimalarial heterocyclic compound of formula I, dimers or pharmaceutically acceptable salt thereof.

Another objective of the present invention is to provide a process for the preparation of heterocyclic compound of formula I, dimers or pharmaceutically acceptable salt thereof.

Still another objective of the present invention is to provide a pharmaceutical composition comprising the heterocyclic compounds of formula I, dimers or pharmaceutically acceptable salt thereof and at least one pharmaceutically acceptable excipient.

Yet another objective of the present invention is to provide a method for treating or preventing malarial infection in a subject in need thereof comprising administering a therapeutically effective amount of a heterocyclic compound of formula I, dimers or pharmaceutically acceptable salt thereof.

SUMMARY OF THE INVENTION

Accordingly, present invention provides a heterocyclic compound of Formula I, dimers or a pharmaceutically acceptable salts thereof

wherein

R¹ and R² may be same or different and each is independently selected from the group consisting of [C1-C50] alkyl, aryl, alkyl aryl, haloalkyl, hydroxy alkyl, alkoxy, hydroxy, halo, cyano, heteroalkyl, heteroaryl, alkyl heteroaryl, substituted or unsubstituted aryl/alkyl, alkenyl, alkenyl aryl, alkenyl heteroaryl, alkynyl, alkynyl aryl, alkynyl heteroaryl, cycloalkyl, heterocycloalkyl, alkyl cycloalkyl, alkyl heterocycloalkyl, alkyl carboxy, acyl, alkyl acyl, alkyl acyloxy, alkyl alkoxy, alkoxycarbonyl, alkyl alkoxycarbonyl, aminocarbonyl, alkyl aminocarbonyl, alkyl acylamino, alkyl ureido, amino, alkyl amino, sulfonyloxy, alkyl sulfonyloxy, sulfonyl, alkyl sulfonyl, sulfinyl, alkyl sulfinyl, alkyl sulfanyl, alkyl sulfonylamino;

R¹ and R² together may form a substituted or unsubstituted cyclic or heterocyclic aromatic ring;

R³ is selected from hydrogen or phenyl sulfonyl (—SO₂Ph).

In an embodiment of the present invention, the heterocyclic compound is selected form the group comprising of:

-   -   a.         N-ethyl-N-((3-(phenylsulfonyl)-3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)         ethanamine (Ia);     -   b. N-((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)-N-ethylethanamine         (Ib);     -   c.         (((3-(phenylsulfonyl)-3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)azanediyl)         dimethanol (Ic);     -   d. (((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)azanediyl)dimethanol         (Id);     -   e.         N-methyl-N-((3-(phenylsulfonyl)-3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)aniline         (Ie);     -   f. N-((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)-N-methyl aniline         (If);     -   g.         4-((3-(phenylsulfonyl)-3H-Pyrrolo[2,3-c]quinolin-4-yl)methyl)morpholine         (Ig);     -   h. 4-((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)morpholine (Ih);     -   i.         N,N-bis((3-(phenylsulfonyl)-3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)aniline         (Ii);     -   j. N,N-bis((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)aniline (Ij);     -   k.         4-methoxy-N-methyl-N-((3-(phenylsulfonyl)-3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)aniline         (Ik);     -   l.         N-((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)-4-methoxy-N-methylaniline         (Il) or     -   m. N⁴-((3H-pyrrolo         [2,3-c]quinolin-4-yl)methyl)-N¹,N¹-diethyl-N⁴-methylpentane-1,4-diamine         (Im).     -   n. 4-methyl-1H-pyrrolo[3,2-c]quinolone (In).

In another embodiment, present invention provides a process for the preparation of compound of Formula I, dimers or pharmaceutically acceptable salt thereof and the said process comprising the steps of:

-   -   i) charging [4-(bromomethyl)-3-(phenylsulfonyl)-3H-pyrrolo         [2,3-c]quinoline of formula 1 and aliphatic amine in a solvent         to obtain a reaction mixture;     -   ii) refluxing the reaction mixture as obtained in step (i) at a         temperature in the range of 70-90° C. for period in the range of         10-14 hr to obtain a solution;     -   iii) charging [4-(bromomethyl)-3-(phenylsulfonyl)-3H-pyrrolo         [2,3-c]quinoline of formula 1, base and aromatic amine in a         solvent to obtain a reaction mixture;     -   iv) refluxing the reaction mixture as obtained in step (iii) at         a temperature in the range of 70-90° C. for period in the range         of 10-14 hr followed by cooling and diluting with water and         extracting the reaction mass into solvent;     -   v) removing the solvent from the solution as obtained in         step (ii) and (iv) under reduced pressure followed by purifying         the crud product with flash silica gel column chromatography         using an eluent to afford compound of formula I having —SO₂Ph as         R₃.     -   vi) charging the compound of formula I having —SO₂Ph as R₃ as         obtained in step     -   v) and base in a solvent to obtain a reaction mixture;     -   vii) refluxing the reaction mixture as obtained in step (vi) at         a temperature in the range of 70-90° C. followed by removing the         solvent under reduced pressure and dissolving the obtained         residue in water and solvent;     -   viii) extracting aqueous layer with solvent followed by washing         the combined organic layer with brine and drying over sodium         sulfate;     -   ix) removing the solvent and purifying to obtain compound of         formula I having —H as R₃.

In yet another embodiment of the present invention, said aliphatic amine is selected from the group comprising of diethylamine (HNEt₂), diethanolamine [HN(CH₂CH₂OH)_(2]) or N¹,N¹-diethylpentane-1,4-diamine.

In yet another embodiment of the present invention, said aromatic amine is selected from the group comprising of

In yet another embodiment of the present invention, said solvent is selected from the group comprising of polar solvents, non-polar solvents, alcohol solvents, ether solvents, ester solvents, and the mixtures thereof.

In yet another embodiment of the present invention, polar solvents is selected from the group comprising of water, ammonia, sulfuric acid, deuterium oxide, ethanol, methanol, acetone, isopropanol, methyl ethyl ketone, n-propanol, acetonitrile, DMSO, DMF and mixtures thereof.

In yet another embodiment of the present invention, Nonpolar solvents is selected from the group comprising of chloroform, pentane, hexane, benzene, toluene, octane, decane, dimethyl ether, and dichloromethane, and mixtures thereof.

In yet another embodiment of the present invention, alcohol solvents is selected from the group comprising of methanol, ethanol, isopropanol, and mixtures thereof. In yet another embodiment of the present invention, ether solvent is selected from the group comprising of tetrahydrofuran, diethyl ether, 1,4-dioxane, methyl tert-butyl ether, and mixtures thereof.

In yet another embodiment of the present invention, ester solvents is selected from the group comprising of methyl acetate, ethyl acetate, isopropyl acetate, tert-butyl acetate, and mixtures thereof.

In yet another embodiment of the present invention, said base is selected from the group comprising of sodium hydroxide, potassium hydroxide, sodium carbonate (Na₂CO₃) or potassium carbonate (K₂CO₃), sodium bicarbonate (NaHCO₃), potassium bicarbonate (KHCO₃).

In another embodiment, present invention provides a process for the preparation of heterocyclic compound, N⁴-((3H-pyrrolo [2,3-c]quinolin-4-yl)methyl)-N¹,N¹-diethyl-N⁴-methylpentane-1,4-diamine, of Formula (Im) and the said process comprising the steps of:

-   -   A) heating the reaction mixture of         4-methyl-3-(phenylsulfonyl)-3H-pyrrolo[2,3-c]quinoline of         formula 2 and selenium dioxide (SeO₂) in a solvent at a         temperature in the range of 60° C. to 80° C. for the period in         the range of 10 to 14 hrs to afford         3-(phenylsulfonyl)-3H-Pyrrolo[2,3-c]quinoline-4-carbaldehyde of         formula 3;

-   -   B) stirring the reaction mixture of step (a) and         N¹,N¹-diethylpentane-1,4-diamine in presence of 4A molecular         sieves in a solvent at temperature in the range of 25 to 30° C.         for the period in the range of 20 to 24 hrs to afford crude         imine of formula 4;

-   -   C) adding sodium borohydride to a cooled solution of crude imine         of step (b) in a solvent followed by refluxing the reaction         mixture at temperature in the range of 60 to 80° C. for the         period in the range of 10 to 20 minutes to afford crude amine of         formula 5;

-   -   D) refluxing the reaction mixture of crude amine of step (c) in         solvent and formaldehyde at temperature in the range of 60 to 80         ° C. for the period in the range of 20 minutes to 30 min         followed by cooling reaction mixture at 0° C. and adding sodium         borohydride (NaBH₄) at 0° C. and stirring the reaction mixture         at a temperature in the range of 25 to 30 ° C. for the period in         the range of 20 to 24 h to afford heterocyclic compound of         formula (Im).

In yet another embodiment, present invention provides a pharmaceutical composition comprising a heterocyclic compound of Formula I, dimers, or pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier, diluent or excipient. In yet another embodiment of the present invention, the said composition is useful as an antimalarial.

In yet another embodiment, present invention provides a method for the treating or preventing malarial infection in a subject in need thereof comprising administering a therapeutically effective amount of a compound formula I dimers, or pharmaceutically acceptable salt thereof.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 represents a process for the preparation of compound of formula I, wherein R₁ and R₂ are same or different and each is independently selected from the group consisting of alkyl, aryl, alkyl aryl, haloalkyl, hydroxy alkyl, alkoxy, hydroxy, halo, cyano, heteroalkyl, heteroaryl, alkyl heteroaryl, substituted or unsubstituted aryl/alkyl, alkenyl, alkenyl aryl, alkenyl heteroaryl, alkynyl, alkynyl aryl, alkynyl heteroaryl, cycloalkyl, heterocycloalkyl, alkyl cycloalkyl, alkyl heterocycloalkyl, alkyl carboxy, acyl, alkyl acyl, alkyl acyloxy, alkyl alkoxy, alkoxycarbonyl, alkyl alkoxycarbonyl, aminocarbonyl, alkyl aminocarbonyl, alkyl acylamino, alkyl ureido, amino, alkyl amino, sulfonyloxy, alkyl sulfonyloxy, sulfonyl, alkyl sulfonyl, sulfinyl, alkyl sulfinyl, alkyl sulfanyl, alkyl sulfonylamino;

-   -   R₁ and R₂ together may form a substituted or unsubstituted         cyclic or heterocyclic aromatic ring;

FIG. 2 represents the process steps for the preparation of heterocyclic compound of Formula (Im).

DETAILED DESCRIPTION OF THE INVENTION

The term “substituted” refers to one or more substituents selected from the group consisting of halogen, hydroxyl, nitro, cyano, thiocyanate, cyanamide, amido, thioamido, sulfonamide, C₁-C₅₀ alkyl, C₂-C₅₀ alkenyl, C₂-C₅₀ alkynyl, C₃-C₅₀ cycloalkyl, ester, thioester, dithioester, ether, thioether, C₆-C₁₈ aryl, heterocycle, peroxide, oxy derivative, thio derivative, acyl derivative, thioketone, sulfonyl derivative or sulfinyl derivative, thiol, nitrate, phosphate ester, thiophosphate ester, sulfate ester, carboxylic acid, phosphonic acid, phosphinic acid, sulfonic acid, amino, ammonium, imine, oxime, diazo, and hydroxamic acid.

The present invention provides an antimalarial heterocyclic compound of formula I, dimers or pharmaceutically acceptable salt thereof

wherein,

R¹ and R² are same or different and each is independently selected from the group consisting of alkyl, aryl, alkyl aryl, haloalkyl, hydroxy alkyl, alkoxy, hydroxy, halo, cyano, heteroalkyl, heteroaryl, alkyl heteroaryl, substituted or unsubstituted aryl/alkyl, alkenyl, alkenyl aryl, alkenyl heteroaryl, alkynyl, alkynyl aryl, alkynyl heteroaryl, cycloalkyl, heterocycloalkyl, alkyl cycloalkyl, alkyl heterocycloalkyl, alkyl carboxy, acyl, alkyl acyl, alkyl acyloxy, alkyl alkoxy, alkoxycarbonyl, alkyl alkoxycarbonyl, aminocarbonyl, alkyl aminocarbonyl, alkyl acylamino, alkyl ureido, amino, alkyl amino, sulfonyloxy, alkyl sulfonyloxy, sulfonyl, alkyl sulfonyl, sulfinyl, alkyl sulfinyl, alkyl sulfanyl, alkyl sulfonylamino;

R¹ and R² together form a substituted or unsubstituted cyclic or heterocyclic aromatic ring;

R³ is selected from the group consisting of hydrogen or phenyl sulfonyl (—SO₂Ph).

The compound of formula I is selected from group comprising of:

-   -   a. N-ethyl-N-((3-(phenylsulfonyl)-3H-pyrrolo         [2,3-c]quinolin-4-yl)methyl)ethanamine [Ia];     -   b. N-((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)-N-ethylethanamine         [Ib];     -   c.         (((3-(phenylsulfonyl)-3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)azanediyl)dimethanol         [Ic];     -   d. (((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)azanediyl)dimethanol         [Id];     -   e.         N-methyl-N-((3-(phenylsulfonyl)-3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)aniline         [Ie];     -   f. N-((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)-N-methyl aniline         [If];     -   g.         4-((3-(phenylsulfonyl)-3H-Pyrrolo[2,3-c]quinolin-4-yl)methyl)morpholine         [Ig];     -   h. 4-((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)morpholine [Ih];     -   i.         N,N-bis((3-(phenylsulfonyl)-3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)aniline         [Ii];     -   j. N,N-bis((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)aniline [Ij];     -   k.         4-methoxy-N-methyl-N-((3-(phenylsulfonyl)-3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)aniline         [Ik];     -   l.         N-((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)-4-methoxy-N-methylaniline         [Il] or     -   m.         N⁴-((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)-N¹,N¹-diethyl-N⁴-methylpentane-1,4-diamine:         [Im]

The present invention provides a process for the preparation of heterocyclic compound of formula I, dimers or pharmaceutically acceptable salt thereof and the said process comprising the step of:

-   -   i. reacting the 4-(bromomethyl)-3-(phenylsulfonyl)-3H-pyrrolo         [2,3-c]quinoline of Formula 1 with aliphatic or aromatic amine         to afford heterocyclic compound of formula I having —SO₂Ph as         R₃;     -   ii. reacting the obtained compound of Formula I having —SO₂Ph as         R₃ with a base to in a solvent to afford the heterocyclic         compound of formula I having —H as R₃.

The process for the preparation of compound of formula I is depicted in FIG. 1.

The process for the preparation of heterocyclic compound of formula I, dimer or pharmaceutically acceptable salt thereof comprising the steps of:

-   -   i) charging [4-(bromomethyl)-3-(phenylsulfonyl)-3H-pyrrolo         [2,3-c]quinoline of formula 1 and amine in a solvent;     -   ii) adding base when amine is aromatic amine;     -   iii) refluxing the reaction mixture at temperature in the range         of 70-90° C. for period in the range of 10-14 hr to obtain a         reaction mixture;     -   iv) cooling the reaction mixture as obtained in step (iii)         followed by diluting the reaction mixture with water and         extracting the reaction mass into solvent when amine is aromatic         amine;     -   v) removing the solvent under reduced pressure;     -   vi) purifying the crud product with flash silica gel column         chromatography using an eluent to afford compound of formula I         having —SO₂Ph as R₃.

Optionally, process further comprise of removal of —SO₂Ph as R₃ to afford the heterocyclic compound of formula I having —H as R₃; wherein said process comprises of:

-   -   vii) charging the compound of formula I having —SO₂Ph as R₃ and         base in a suitable solvent;     -   viii) refluxing the reaction mixture at a 70-90° C. for a period         of 1 hr;     -   ix) removing the solvent under reduced pressure and dissolving         the obtained residue in water and solvent;     -   x) extracting aqueous layer with solvent;     -   xi) washing the combined organic layer with brine and drying         over sodium sulfate;     -   xii) removing the solvent under 200 mbar pressure at 50° C.; and     -   xiii) purifying the obtained crude product with flash silica gel         column chromatography using an eluent (Pet.         Ether/ethylacetate/DCM/Methanol) to afford compound of formula I         having —H as R₃.

The solvent used at step (i) is selected from the group consisting of polar aprotic solvent, polar protic solvent, polar solvent, non-polar solvent or mixtures thereof.

Polar aprotic solvent is selected from the group consisting of N-methylpyrrolidone, tetrahydrofuran, ethyl acetate, acetone, dimethyl formamide, acetonitrile, dimethyl sulfoxide, propylene carbonate or mixtures thereof.

Polar protic solvent is selected from the group consisting of Formic acid, n-butanol, isopropanol, nitromethane, ethanol, methanol, acetic acid, water or mixtures thereof.

Polar aprotic solvent used instep (i) is more particularly dry tetrahydrofuran or acetonitrile. The aliphatic amine is selected from the group consisting of diethylamine (HNEt₂), diethanolamine [HN(CH₂CH₂OH)_(2]) or N¹,N¹-diethylpentane-1,4-diamine.

The aromatic amine is selected from the group consisting of aniline, N-methyl aniline, N-methyl p-anisidine, morpholine.

Base used is selected from the group consisting of sodium hydroxide, potassium hydroxide, sodium carbonate (Na₂CO₃) or potassium carbonate (K₂CO₃), sodium bicarbonate (NaHCO₃), potassium bicarbonate (KHCO₃), preferably sodium carbonate (Na₂CO₃) is used at step (ii) and potassium carbonate (K₂CO₃) is used at step (viii).

Temperature to conduct the reaction at step (ii), is in the range of 70° C. to 90° C., more particularly the temperature is 70° C. when dry tetrahydrofuran (THF) and 80° C. when acetonitrile is used.

Organic solvent used at steps (v) and (x) for extraction is selected from ester solvent, ketone solvent, non-polar solvent, or mixtures thereof, preferably ester solvents.

Ketone solvent used in selected from the group consisting of acetone, methyl propionone, ethyl propionone, n-butanone, methyl isobutyl ketone, and mixtures thereof.

Ester solvents used in selected from the group consisting of methyl acetate, ethyl acetate, isopropyl acetate, tert-butyl acetate, and mixtures thereof preferably ethyl acetate.

Non-polar solvents used in selected from the group consisting of chloroform, pentane, hexane, benzene, toluene, octane, decane, dimethyl ether, and dichloromethane, and mixtures thereof. Solvent used at step (viii) is selected from the group consisting of the polar solvents, non-polar solvents, alcohol solvents, ether solvents, ester solvents, amide solvents and the mixtures thereof.

Polar solvents is selected from the group consisting of water, ammonia, sulfuric acid, deuterium oxide, ethanol, methanol, acetone, isopropanol, methyl ethyl ketone, n-propanol, acetonitrile, DMSO, and DMF and mixtures thereof.

Non-polar solvents is selected from the group consisting of chloroform, pentane, hexane, benzene, toluene, octane, decane, dimethyl ether, and dichloromethane, and mixtures thereof. An alcohol solvent is selected from the group consisting of methanol, ethanol, isopropanol, and mixtures thereof. Ether solvents may include tetrahydrofuran, diethyl ether, 1,4-dioxane, methyl tert-butyl ether, and mixtures thereof.

Ester solvents is selected from the group consisting of methyl acetate, ethyl acetate, isopropyl acetate, tert-butyl acetate, and mixtures thereof.

In particularly useful embodiments, alcohol solvents are used and most preferably methanol is used as a solvent in step (viii).

Temperature to reflux the reaction mixture at step ix) is in the range of 65° C.-85° C., more preferably at 70° C.

Present invention provides a process for the synthesis of heterocyclic compound N⁴-((3H-pyrrolo [2,3-c]quinolin-4-yl)methyl)-N¹,N¹-diethyl-N⁴-methylpentane-1,4-diamine of Formula (Im) wherein R₁ or R₂ is heteroalkyl. The process is depicted in FIG. 2.

The process for the synthesis of heterocyclic compound N⁴-((3H-pyrrolo [2,3-c]quinolin-4-yl)methyl)-N¹,N¹-diethyl-N⁴-methylpentane-1,4-diamine of Formula (Im) wherein R₁ or R₂ is heteroalkyl comprises of the following steps:

-   -   a) heating the reaction mixture of         4-methyl-3-(phenylsulfonyl)-3H-pyrrolo[2,3-c]quinoline of         formula 2 and selenium dioxide (SeO₂) in a solvent at a         temperature in the range of 60° C. to 80° C. for the period in         the range of 10 to 14 hrs to afford         3-(phenylsulfonyl)-3H-Pyrrolo[2,3-c]quinoline-4-carbaldehyde of         formula 3;     -   b) stirring the reaction mixture of step (a) and         N¹,N¹-diethylpentane-1,4-diamine in presence of 4 Å molecular         sieves in a solvent at temperature in the range of 25 to 30° C.         for the period in the range of 20 to 24 hrs to afford crude         imine of formula 4;     -   c) adding sodium borohydride to a cooled solution of crude imine         of step (b) in a solvent followed by refluxing the reaction         mixture at temperature in the range of 60 to 80° C. for the         period in the range of 10 to 20 minutes to afford crude amine of         formula 5;     -   d) refluxing the reaction mixture of crude amine of step (c) in         solvent and formaldehyde at temperature in the range of 60 to 80         ° C. for the period in the range of 20 minutes to 30 min         followed by cooling reaction mixture at 0° C. and adding sodium         borohydride (NaBH₄) at 0° C. and stirring the reaction mixture         at room temperature in the range of 25 to 30 ° C. for the period         in the range of 20 to 24 h to afford heterocyclic compound of         formula (Im).

Suitable solvent used at steps a), b), c), and d) may include the polar solvents, non-polar solvents, alcohol solvents, ether solvents, ester solvents, amide solvents and the mixtures thereof. Polar solvents may include water, ammonia, sulfuric acid, deuterium oxide, ethanol, methanol, acetone, isopropanol, methyl ethyl ketone, n-propanol, acetonitrile, DMSO, and DMF and mixtures thereof. Non-polar solvents include chloroform, pentane, hexane, benzene, toluene, octane, decane, dimethyl ether, and dichloromethane, and mixtures thereof. Suitable alcohol solvents may include methanol, ethanol, isopropanol, and mixtures thereof. Suitable ether solvents include tetrahydrofuran, diethyl ether, 1,4-dioxane, methyl tert-butyl ether, and mixtures thereof. Suitable ester solvents include methyl acetate, ethyl acetate, isopropyl acetate, tert-butyl acetate, and mixtures thereof. In particularly useful embodiments, ether solvents are used at step a) and most preferably 1, 4-dioxane is used as a solvent at step a).

Non-polar solvents are used at step b) and most preferably toluene is used as a solvent at step b).

Alcohol solvents are used at step c) and d), and most preferably methanol is used as a solvent at step c) and d).

The present invention provides a pharmaceutical composition comprising a heterocyclic compound of formula I, dimers thereof or a stereoisomer, or ester or pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier, diluent or excipient.

The pharmaceutical compositions of the invention may be prepared by combining a compound of the invention with an appropriate pharmaceutically acceptable carrier, diluent or excipient, and may be formulated into preparations in solid, semi-solid, liquid or gaseous forms, such as tablets, capsules, powders, granules, ointments, solutions, injections, gels and microspheres. The present invention relates to administering ‘an effective amount’ of the ‘composition of invention’ to the subject suffering from said disease. Accordingly, heterocyclic compound of formula I, dimers thereof and pharmaceutical compositions containing them may be administered using any amount, any form of pharmaceutical composition via any route of administration effective for treating the disease. Typical routes of administering such pharmaceutical compositions include, without limitation, oral, topical, transdermal, inhalation, parenteral, sublingual, buccal, rectal, vaginal, and intranasal.

Pharmaceutical compositions of the invention are formulated so as to allow the active ingredients contained therein to be bioavailable upon administration of the composition to a patient. Compositions that will be administered to a subject or patient may take the form of one or more dosage units. The dosage forms can also be prepared as sustained, controlled, modified and immediate dosage forms.

The present invention provides a method for the treating or preventing malarial infection in a subject in need thereof; comprising administering to the said subject a therapeutically effective amount of the heterocyclic compound of formula I, dimers thereof or a pharmaceutically acceptable salt thereof.

EXAMPLES

The following examples are given by way of illustration and therefore should not be construed to limit the scope of the invention.

Procedure A: Aliphatic Amines

A dry single-neck round-bottom flask was charged with [4-(bromomethyl)-3-(phenylsulfonyl)-3H-pyrrolo [2,3-c]quinoline of formula 1 (0.25 mmol, 1 equiv.) and aliphatic amines of formula A or B (2.50 mmol, 10 equiv.). To this mixture, dry THF was added (4 mL) and reaction mixture was refluxed at 70° C. for 12 h. After completion of the reaction solvent was removed under reduced pressure and crude reaction mixture was purified using flash silica gel column chromatography using DCM/MeOH as eluents to obtain the pure compounds [1a] and [1c] of formula I respectively.

Procedure B: Aromatic Amines

In a dry two-neck round-bottom flask containing 4-(bromomethyl)-3-(phenylsulfonyl)-3H-pyrrolo [2,3-c]quinoline of formula 1 (0.25 mmol, 1 equiv.), aromatic amine C-F (0.38 mmol, 1.5 equiv.) and Na₂CO₃ (1.25 mmol, 5 equiv.) were charged with dry acetonitrile (4 mL) via syringe. This mixture was refluxed at 80° C. for 12 h. After completion of reaction, it was cooled to room temperature (25° C.) and diluted with water (20 mL) and ethyl acetate (20 mL). Organic layer separated and aqueous layer was extracted with ethyl acetate (15 mL×2). Combined organic layer was washed with brine (10 mL×2) and dried over sodium sulphate. Solvent was removed under reduced pressure and crude product was purified using flash silica gel column chromatography using petroleum ether/EtOAc as eluents to obtain the desired compounds [Ie], [Ig], [Ii] and [Ik] of Formula I respectively.

Procedure C: For —SO₂Ph Deprotection

A dry single-neck round-bottom flask charged with compound of Formula I (Ia, Ic, Ie, Ig, Ii, Ik,) (0.12 mmol, 1 equiv.), K₂CO₃ (0.36 mmol, 3 equiv.) and methanol (5 mL) and this mixture was refluxed at 70° C. for 1 h. After completion of reaction solvent was removed under reduced pressure and residue was dissolved in water (10 mL) and ethyl acetate (10 mL). Organic layer separated and aqueous layer washed with ethyl acetate (10 mL×2). Combined organic layer were washed with brine (10 mL) and dried over sodium sulphate. Solvent was removed under reduced pressure and crude product was purified using flash silica gel column chromatography using suitable eluents to furnish desired compounds [Ib], [Id], [If], [Ih] [Ij] and [Il] of Formula I respectively.

Example 1 N-ethyl-N-((3-(phenylsulfonyl)-3H-pyrrolo [2,3-c]quinolin-4-yl)methyl)ethanamine [Ia]

Following general experimental procedure A, [1a] is obtained as brown oil (76 mg, 77%); R_(f)=0.5 (19:1 DCM/MeOH); ¹H NMR (400 MHz, CDCl₃): δ 1.24 (t, J=7.2 Hz, 6H), 3.42 (q, J=7.1 Hz, 4H), 4.78 (s, 2H), 7.32 (d, J=3.6 Hz, 1H), 7.56 (t, J=7.3 Hz, 2H), 7.64 (dd, J=7.3 Hz, 2H), 7.71 (t, J=7.3 Hz, 1H), 7.80 (d, J=7.9 Hz, 2H), 8.05 (d, J=3.6 Hz, 1H), 8.14 (d, J=7.9 Hz, 1H), 8.28 (d, J=7.9 Hz, 1H); ¹³C NMR (100 MHz, CDCl₃):δ9.6, 48.8, 53.6, 106.8, 121.9, 122.8, 126.1, 126.6, 127.8, 128.9, 129.3 129.6, 130.2, 132.3, 134.8, 136.2, 138.1, 142.3; HRMS (ESI−TOF) (m/z): [M+H]⁺Calcd for C₂₂H₂₄N₃O₂S 394.1584;Found 394.1582.

Example 2 N-((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)-N-ethylethanamine [Ib]

Following general experimental procedure C, [1b] obtained as brown oil (26 mg, 87%); R_(f)=0.6 (9:1 DCM/MeOH); ¹H NMR (400 MHz, CDCl₃): δ 1.15 (t, J=7.3 Hz, 6H), 2.71 (q, J=7.3 Hz, 4H), 4.24 (s, 2H), 7.04 (d, J=2.4 Hz, 1H), 7.42 (d, J=3.1 Hz, 1H), 7.52-7.61 (m, 2H), 8.11 (d, J=7.3 Hz, 1H), 8.20 (d, J=8.6 Hz, 1H), 10.90 (bs, 1H); ¹³C NMR (100 MHz, CDCl₃):δ 11.8, 47.7, 60.6, 100.9, 122.8, 123.4, 125.2, 125.4, 125.8, 128.4, 128.8, 129.0, 142.4, 147.3; HRMS (ES−TOF) (m/z):[M+H]⁺Calcd for C₁₆H₂₀N₃ 254.1650; Found 254.1652.

Example 3 (((3-(phenylsulfonyl)-3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)azanediyl)dimethanol [Ic]

Following general experimental procedure A, [1c] obtained as pale yellow solid (42 mg, 40%); R_(f)=0.3 (9:1 DCM/MeOH); Mp=98-99° C.; ¹H NMR (400 MHz, CDCl₃): δ 2.86 (t, J=4.8 Hz, 4H), 3.40 (t, J=4.8 Hz, 4H), 4.37 (s, 2H), 4.95 (bs, 2H), 7.31 (d, J=3.6 Hz, 1H), 7.50 (t, J=7.9 Hz, 2H), 7.62 (dd, J=7.3 Hz, 2H), 7.68 (d, J=7.9 Hz, 3H), 8.07-8.15 (m, 3H); ¹³C NMR(100 MHz, CDCl₃):δ58.6, 59.1, 59.9, 106.4, 121.9, 122.9, 126.3, 126.9, 127.1, 128.3, 128.9, 129.8, 132.8, 134.4, 136.0, 139.1, 142.7, 148.9;HRMS (ESI−TOF) (m/z):[M+H]⁺Calcd for C₂₂H₂₄N₃O₄S 426.1482;Found 426.1480.

Example 4 (((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)azanediyl)dimethanol [Id]

Following general experimental procedure C, [1d] obtained as brown sticky solid (25 mg, 74%); R_(f)=0.5(4:1 DCM/MeOH); ¹H NMR (500 MHz, MeOD₄): δ 2.88 (t, J=5.8 Hz, 4H), 3.72 (t, J=5.7Hz, 4H), 4.34 (s, 2H), 7.13 (d, J=3.1 Hz, 1H), 7.60 (dd, J=4.6 Hz, 2H) 7.62 (d, J=2.6 Hz, 1H), 8.06 (dd, J=5.3 Hz, 1H), 8.28 (dd, J=4.2 Hz, 1H); ¹³C NMR(125 MHz, MeOD₄): δ 58.2, 60.3, 60.6, 101.7, 124.2, 124.9, 126.9, 127.1, 128.2, 129.0, 129.2, 130.8, 142.1, 149.4; HRMS (ESI−TOF) (m/z):[M+H]⁺Calcd for C₁₆H₂₀N₃O₂ 286.1550; Found 286.1552.

Example 5 N-methyl-N-((3-(phenylsulfonyl)-3H-pyrrolo[2,3-c] quinolin-4-yl)methyl)aniline [Ie]

Following general experimental procedure B, [le] obtained as white solid (40 mg, 38%); R_(f)=0.6 (4:1 Petroleum ether/EtOAc); Mp=146-148° C.; ¹H NMR (400 MHz, CDCl₃): δ 3.16 (s, 3H), 5.08 (s, 2H),6.36 (d, J=8.5 Hz, 2H), 6.56 (t,J=7.3 Hz, 1H), 7.01 (t, J=7.9, 2H), 7.31 (d, J=3.1 Hz, 1H), 7.47-7.60 (m, 4H), 7.64 (t, J=7.3 Hz, 1H), 7.72 (d, J=7.9 Hz, 2H), 7.92 (d, J=7.3 Hz, 1H), 8.06-8.13 (m, 2H); ¹³C NMR (100 MHz, CDCl₃):δ39.9, 56.8, 106.2, 111.9, 115.6, 121.7, 122.6, 126.4, 126.5, 127.5, 127.8, 128.7, 129.8, 129.9, 131.6, 134.2, 135.1, 139.3, 143.3, 146.0, 149.8;HRMS (ESI−TOF) (m/z):):[M+H]⁺Calcd for C₂₅H₂₂N₃O₂S 428.1427; Found 428.1421.

Example 6 N-((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)-N-methyl aniline [If]

Following general experimental procedure C, [1f] obtained as white solid (32 mg, 94%); R_(f)=0.6 (7:3 Petroleum ether/EtOAc); Mp=139-141 ° C.; ¹H NMR (400 MHz, CDCl₃): δ 2.99 (s, 3H), 4.99 (s, 2H),6.92 (t, J=7.3 Hz, 1H), 7.01-7.12 (m, 3H), 7.29-7.40 (m, 3H), 7.56-7.69 (m, 2H), 8.16 (d, J=7.9 Hz, 1H), 8.22 (d, J=7.9 Hz, 1H), 9.46 (bs, 1H); ¹³C NMR (100 MHz, CDCl₃):δ39.2, 60.8, 101.3, 114.9, 119.4, 122.9, 123.4, 125.7, 125.9, 126.1, 127.8, 129.0, 129.2, 129.7, 142.4, 146.7, 150.5; HRMS (ESI−TOF) (m/z):[M+H]⁺Calcd for C₁₉H₁₈N₃ 288.1495; Found 288.1491.

Example 7 4-((3-(phenylsulfonyl)-3H-Pyrrolo[2,3-c]quinolin-4-yl)methyl)morpholine [Ig]

Following general experimental procedure B, [1g] obtained as White solid (43 mg, 43%); R_(f)=0.3 (1:1Petroleum ether/EtOAc); Mp=138-140 ° C.; ¹H NMR (500 MHz, CDCl₃): δ 2.56 (s, 4H), 3.60 (s, 4H), 4.28 (s, 2H), 7.28 (s, 1H), 7.46 (t, J=8.0 Hz, 2H), 7.55-7.64 (m, 2H), 7.69 (t, J=8.0 Hz, 1H), 7.81 (d, J=7.6 Hz, 2H), 7.99 (d, J=3.4 Hz, 1H), 8.13 (d, J=8.0 Hz, 1H), 8.17 (d, J=8.4 Hz, 1H); ¹³C NMR(125 MHz, CDCl₃):δ53.7, 63.7, 66.8, 106.7, 121.8, 122.8, 126.4, 126.7, 128.1, 128.6, 129.4, 129.5, 132.6, 133.9, 135.6, 139.6, 143.0, 146.1; HRMS (ESI−TOF) (m/z):):[M+H]⁺Calcd for C₂₂H₂₂N₃O₃S 408.1376; Found 408.1372.

Example 8 4-((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)morpholine [Ih]

Following general experimental procedure C, [1h] obtained as White solid (28 mg, 88%); R_(f)=0.3 (9:1 DCM/MeOH); Mp=148-150° C.; ¹H NMR (400 MHz, CDCl₃): δ 2.64 (s, 4H), 3.80 (s, 4H), 4.17 (s, 2H), 7.06 (d, J=1.8 Hz, 1H), 7.44 (d, J=1.8 Hz, 1H), 7.53-7.62 (m, 2H), 8.12 (d, J=7.9 Hz, 1H), 8.20 (d, J=7.3 Hz, 1H), 10.49 (bs, 1H); ¹³C NMR (100 MHz, CDCl₃):δ54.0, 65.4, 67.1, 101.3, 122.8, 123.4, 125.4, 125.7, 126.0, 128.3, 128.5, 129.1, 142.4, 145.5; HRMS (ESI−TOF) (m/z):):[M+H]⁺Calcd for C₁₆H₁₈N₃O 268.1444; Found 268.1442.

Example 9 N,N-bis((3-(phenylsulfonyl)-3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)aniline [Ii]

Following general experimental procedure B, [1i] obtained as Brown solid (45 mg, 25%); R_(f)=0.3 (3:2 Petroleum ether/EtOAc); Mp=188-190° C.; ¹H NMR (400 MHz, CDCl₃): δ 5.21 (s, 4H), 6.29 (d, J=7.9 Hz, 2H),6.51 (t, J=7.3 Hz, 1H), 6.90 (t,J=7.9 Hz, 2H), 7.03 (t, J=7.9 Hz, 4H), 7.24 (t, J=7.3 Hz, 2H), 7.31 (d, J=3.6 Hz, 2H), 7.55-7.65 (m, 6H), 7.68 (t, J=7.3 Hz, 2H), 8.07 (d, J=3.6 Hz, 2H), 8.15 (t, J=7.9 Hz, 4H); ¹³C NMR (100 MHz, CDCl₁₃):δ55.8, 105.7, 112.1, 115.4, 121.9, 122.7, 126.4, 127.4, 127.8, 128.4, 129.3, 130.1, 131.4, 133.8, 134.8, 139.0, 143.5, 146.5, 150.4, 157.6; HRMS (ESI−TOF) (m/z):):[M+H]⁺Calcd for C₄₂H₃₂N₅O₄S₂ 734.1890; Found 734.1876.

Example 10 N,N-bis((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)aniline [Ij]

Following general experimental procedure C, [1j] obtained as Brown solid (30 mg, 55%); R_(f)=0.3 (3:7 Petroleum ether/EtOAc); Mp=242-244° C.; ¹H NMR (400 MHz, DMSO-d₆): δ 5.36 (s, 4H), 6.59 (t, J=7.3 Hz, 1H), 6.71 (d, J=8.5 Hz, 2H), 6.95 (t, J=7.3 Hz, 2H), 7.25 (s, 2H), 7.56-7.67 (m, 4H), 7.89 (s, 2H), 8.18 (d, J=7.9 Hz, 2H), 8.34 (d, J=7.9 Hz, 2H), 13.35 (bs, 2H); ¹³C NMR (100 MHz, DMSO-d₆):δ60.2, 101.3, 114.9, 118.5, 123.4, 123.5, 125.7, 126.1, 126.9, 128.1, 128.4, 128.6, 128.8, 141.6, 148.2, 150.9; HRMS (ESI−TOF) (m/z):[M+H]⁺Calcd for C₃₀H₂₄N₅ 454.2026; Found 454.2020.

Example 11 4-methoxy-N-methyl-N-4-((3-(phenylsulfonyl)-3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)aniline [Ik]

Following general experimental procedure B, [1k] obtained as yellow solid (52 mg, 45%); R_(f)=0.8 (4:1 Petroleum ether/EtOAc); Mp=48-50° C.; ¹H NMR (400 MHz, CDCl₃): δ 3.05 (s, 3H), 3.70 (s, 3H), 5.03 (s, 2H), 6.39 (d, J=9.2 Hz, 2H), 6.64 (d, J=9.2 Hz, 2H), 7.30 (d, J=3.7 Hz, 1H), 7.45-7.65 (m, 5H), 7.70 (d, J=7.3 Hz, 2H), 7.95 (d, J=7.3 Hz, 1H), 8.05-8.13 (m, 2H); ¹³C NMR (100 MHz, CDCl₃):δ40.3, 55.7, 57.6, 106.1, 113.7, 114.3, 121.7, 122.6, 126.3, 126.5, 127.6, 127.8, 129.7, 129.8, 131.7, 134.1, 135.1, 139.3, 143.3, 144.7, 146.5, 151.0; HRMS (ESI−TOF) (m/z):):[M+H]⁺Calcd for C₂₆H₂₄N₃O₃S 458.1533; Found 458.1524.

Example 12 N-((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)-4-methoxy-N-methylaniline [Il]

Following general experimental procedure C, [1l] obtained as Brown oil (27 mg, 71%); R_(f)=0.5 (7:1 Petroleum ether/EtOAc); ¹H NMR (400 MHz, CDCl₃): δ 2.92 (s, 3H), 3.79 (s, 3H), 4.86 (s, 2H), 6.89 (d, J=8.5 Hz, 2H), 7.00-7.10 (m, 3H), 7.34 (s, 1H), 7.55-7.64 (m, 2H), 8.15(d, J=7.9 Hz, 1H), 8.21 (d, J=7.3 Hz, 1H), 9.81 (bs, 1H); ¹³C NMR (100 MHz, CDCl₃):δ40.9, 55.6, 62.3, 101.2, 114.9, 117.7, 122.9, 123.4, 125.7, 125.8, 126.1, 128.0, 128.9, 129.0, 142.4, 145.2, 146.8, 153.8; HRMS (ESI−TOF) (m/z):):[M+H]⁺Calcd for C₂₀H₂₀N₃O 318.1601; Found 318.1596.

Example 13 N⁴-((3H-pyrrolo [2,3-c]quinolin-4-yl)methyl)-N¹,N¹-diethyl-N⁴-methylpentane-1,4-diamine of Formula (Im)

a) 3-(phenylsulfonyl)-3H-Pyrrolo[2,3-c]quinoline-4-carbaldehyde (3)

A dry single-neck round-bottom flask was charged with 4-methyl-3-(phenylsulfonyl)-3H-pyrrolo[2,3-c] quinolone of formula 2 (500 mg, 1.55 mmol) and SeO₂ (188 mg, 1.70 mmol) under argon atmosphere. 1, 4-dioxane (5 mL) was added via syringe and reaction mixture heated at 60° C. for 12 h under argon atmosphere. After this time, solvent was removed under reduced pressure and crude reaction mixture was diluted with ethyl acetate (20 mL) and water (20 mL). Then, organic layer was separated and aqueous layer extracted with ethyl acetate (20 mL×2). Combined organic layer was washed using brine (20 mL) and dried over sodium sulphate. Evaporation of solvent provided crude product, which was purified using flash silica gel column chromatography (9:1 Petroleum ether/EtOAc) to obtained desired aldehyde as pale yellow solid (410 mg, 78%).

R_(f)=0.5 (4:1 Petroleum ether/EtOAc); Mp=173-175° C.; ¹H NMR (500 MHz, CDCl₃): δ 7.34 (d, J=3.6 Hz, 1H), 7.51 (t, J=7.3 Hz, 2H), 7.62 (t, J=7.3 Hz, 1H), 7.69-7.80 (m, 2H), 7.86 (d, J=7.9 Hz, 2H), 8.00 (d, J=3.6 Hz, 1H), 8.18 (d, J=7.9 Hz, 1H), 8.31 (d, J=8.5 Hz, 1H), 10.55 (s, 1H); ¹³C NMR (125 MHz, CDCl₃): δ 107.5, 123.1, 123.5, 125.4, 126.9, 128.9, 129.3, 130.7, 132.1, 134.3, 135.9, 138.1, 143.0, 143.2, 190.2; HRMS (ESI−TOF) (m/z):):[M+Na]⁺Calcd for C₁₈H₁₂N₂O₃SNa 359.0461; Found 359.0455.

b) N⁴-((3H-pyrrolo [2,3-c]quinolin-4-yl)methyl)-N¹,N¹-diethyl-N⁴-methylpentane-1,4-diamine

In a flame dried single-neck round-bottom flask containing 10-20 freshly activated molecular sieves (4 Å) and 3-(phenylsulfonyl)-3H-Pyrrolo[2,3-c]quinoline-4-carbaldehyde (3, 100 mg, 0.29 mmol) was added dry toluene (2-3 mL) via syringe. N¹,N¹-diethylpentane-1,4-diamine (117 μL, 0.59 mmol) was added and mixture was stirred at 28 ° C. for 24 h. After this time, reaction mixture was filtered over celite and celite layer washed with ethyl acetate (10 mL×2). Combined filtrate was concentrated under reduced pressure and obtained crude imine (4), which was used as it is for further transformation.

Crude imine of formula 4 (140 mg, 0.29 mmol) dissolved in methanol (4 mL) was cooled at 0° C. and NaBH₄ (33 mg, 0.88 mmol) was added. Then, reaction mixture was warmed to 28° C. and then refluxed at 70° C. for 15 minutes. Water (20 mL) was added in mixture and it was extracted with EtOAc (15 mL×2). Organic layer washed with brine (10 mL) and dried over sodium sulphate. Solvent was removed under reduced pressure and crude amine (5) used for further reaction.

Crude amine of formula 5 (100 mg, 0.21 mmol) was dissolved in methanol (2 mL) and it was treated with formaldehyde (41% aqueous solution, 75 1.04 mmol). The solution was heated under at 70° C. for 30 min, after cooling in ice bath NaBH₄ (28 mg, 0.83 mmol) was added in small portions, and this mixture was stirred at 28° C. for 24 h. Solvent was evaporated under reduced pressure and residue was dissolved in DCM and saturated ammonium chloride solution. Organic layer was separated and aqueous layer extracted with DCM (20 mL×2). Combined organic layer washed with brine (20 mL) and dried over sodium sulphate. The crude product was subjected to flash silica gel column chromatography using NH₄OH: MeOH: DCM (2:2:96 to 2:4:94) v/v to obtain compound of Formula (Im) as yellow oil (25 mg, 34%).

R_(f)=0.5 (4:1 DCM/MeOH); ¹H NMR (400 MHz, CDCl₃): δ 1.04 (t, J=7.3 H, 6H), 1.14 (d, J=6.1 Hz, 3H), 1.38-1.50 (m, 1H), 1.55-1.64 (m, 2H), 1.65-1.76 (m, 1H), 2.26 (s, 3H), 2.42-2.51 (m, 2H), 2.56 (q, J=6.7 Hz, 4H), 2.85-2.97 (m, 1H), 4.22 (q, J=14.6 Hz, 2H), 7.03 (d, J=3.1 Hz, 1H), 7.41 (d, J=2.4 Hz, 1H), 7.50-7.60 (m, 2H), 8.11 (d, J=7.9 Hz, 1H), 8.20 (d, J=7.9 Hz, 1H), 10.71 (bs, 1H); ¹³C NMR (100 MHz, CDCl₃):δ11.5, 13.4, 24.9, 31.8, 36.6, 46.8, 52.9, 58.7, 60.8, 100.9, 122.8, 123.4, 125.3, 125.4, 125.8, 128.4, 128.5, 129.0, 142.4, 147.5; HRMS (ESI−TOF) (m/z):):[M+H]⁺Calcd for C₂₂H₃₃N₄ 353.2700; Found 353.2694.

Example 13 4-methyl-1H-pyrrolo[3,2-c]quinoline compound of formula [In]

Following general experimental procedure C, Formula In obtained as White solid (19 mg, 86%); R_(f)=0.2 (1:1 Petroleum ether/EtOAc); Mp=233-235° C.; ¹H NMR (400 MHz, Acetone-d₆): δ 2.86 (s, 3H), 7.15 (d, J=3.1 Hz, 1H), 7.48-7.56 (m, 2H), 7.61 (d, J=3.1 Hz, 1H), 8.03 (d, J=7.3 Hz, 1H), 8.25 (dd, J=2.4, 7.9 Hz, 1H); ¹³C NMR (100 MHz, Acetone-d₆):δ21.2, 101.9, 123.7. 124.1, 125.6, 126.0, 127.1, 128.3, 129.7, 143.7, 146.8; HRMS (ESI−TOF) (m/z):):[M+H]⁺Calcd for C₁₂H₁₁N₂ 183.0917; Found 183.0916.

Example 15 Antimalarial Activity Methods Plasmodium Culture

Plasmodium falciparum 3D7 strain from Malaria Research and Reference Reagent Resource Center (ID NO: MRA-102). Plasmodium falciparum (3D7) is cultured in the laboratory as per standard protocols [AzarRadfar, Darío Méndez, Carlos Moneriz, María Linares, Patricia Marín-García, Antonio Puyet, AmaliaDiez & José M Bautista. Synchronous culture of Plasmodium falciparum at high parasitemia levels Nature Protocols 2009, 4, 1899-1915]. When the parasitemia (i.e., percent infection of human RBCs) reaches >15%, 1 mL of culture suspension is layered over 10 mL of 60% percoll (pH and osmolality adjusted using PBS) and centrifuged at 3000 rpm for 5 min using a swing out rotor. This separates late stage parasite (trophozoite and schizont) infected RBC (as a band on top of the percoll cushion) from early stage parasite (ring) infected and uninfected RBCs (as pellet at the bottom of the percoll cushion). The >90% enriched late stage parasite infected RBCs are collected, washed with complete RPMI media and added to a 2% hematocrit RBC suspension such that the final parasitemia is around 2%. The parasites grow in a synchronous manner for at least 2 rounds of asexual cycle (48 hours). This culture is then used for anti-malarial screening as given below.

Anti-Malarial Screen

200 μL of ring stage parasite culture at -2% parasitemia (see above) is added to each well in a 96 well plate pre-seeded with the compound of interest at the required concentration. 1 mM and 10 mM stocks dilutions of the compounds are prepared in cell culture grade DMSO, and the final concentration used in the assay is either 10 μM (for identifying molecules affecting parasite growth) or a serial dilution from 10 μM to 1 nM (for estimating the dose response and EC₅₀ value). All compounds are plated in triplicates as biological replicates. Each 96 well plate also includes negative control (compound untreated & DMSO only treated culture) and positive control (standard anti-malarial compounds treated culture). Standard anti-malarials used are chloroquine, artemisinine and atovaquone, each at 1μM concentration although their respective IC₅₀s are >20 nM for the 3D7 strain of P. falciparum. After plating, the culture is incubated in standard growth condition for 60 hours, after which the cultures are processed for testing the effect of compounds on parasite growth as given below.

Estimating Parasite Growth by SybrGreen Staining

The inventors have standardized a SybrGreen dye based staining protocol for estimating parasite growth, which is a modification of previously published protocol [Plouffe et.al, 2008]. SybrGreen dye binds to DNA and only the DNA bound dye gives a specific fluorescence emission (520 nM) when excited (498 nM). Since only the parasites have DNA (as human RBCs are devoid of nucleus), the SybrGreensignal is a direct indictor of parasite growth. A standard fluorescent plate reader issued for assay read out, and the staining is done as follows. 25 μL of 10× stock containing of dye and Triton X100 (0.5%) is added to each of 200 μL culture growing in a 96 well plate and mixed well and incubated for 15 min-30 min before reading fluorescence emission using the plate reader at the appropriate wavelength.

Data from Anti-Malarial Screening

The table below provides the results from the anti-malarial screening experiment. First the growth inhibition assay was carried out in which the molecules were tested against the parasite at 10 μM concentration. ≥80% growth inhibition was seen in case of all molecules, except compound of formula Ie & NCLite-M1. So the dose response was carried out for all molecules and the EC₅₀ values are given. Compounds active in nanomolar range are highlighted.

ADVANTAGES OF THE INVENTION

1. New heterocyclic compound of formula I is disclosed which are used for the treatment of malarial infection.

2. Simple and cost-effective process for the preparation of compound of formula I.

3. These compounds due to their unique aromatic and multifunctional amine groups may be very good G-quadruplex binding agents, which is a requirement for anticancer drugs. 

1. A heterocyclic compound of Formula I, dimers or a pharmaceutically acceptable salts thereof

wherein R¹ and R² may be same or different and each is independently selected from the group consisting of [C1-C50] alkyl, aryl, alkyl aryl, haloalkyl, hydroxy alkyl, alkoxy, hydroxy, halo, cyano, heteroalkyl, heteroaryl, alkyl heteroaryl, substituted or unsubstituted aryl/alkyl, alkenyl, alkenyl aryl, alkenyl heteroaryl, alkynyl, alkynyl aryl, alkynyl heteroaryl, cycloalkyl, heterocycloalkyl, alkyl cycloalkyl, alkyl heterocycloalkyl, alkyl carboxy, acyl, alkyl acyl, alkyl acyloxy, alkyl alkoxy, alkoxycarbonyl, alkyl alkoxycarbonyl, aminocarbonyl, alkyl aminocarbonyl, alkyl acylamino, alkyl ureido, amino, alkyl amino, sulfonyloxy, alkyl sulfonyloxy, sulfonyl, alkyl sulfonyl, sulfinyl, alkyl sulfinyl, alkyl sulfanyl, alkyl sulfonylamino; R¹ and R² together may form a substituted or unsubstituted cyclic or heterocyclic aromatic ring; R³ is selected from hydrogen or phenyl sulfonyl (—SO₂Ph).
 2. The heterocyclic compound as claimed in claim 1, wherein said compound is selected form the group comprising of: a. N-ethyl-N-((3-(phenylsulfonyl)-3H-pyrrolo[2,3-c]quinolin-4-yl)methyl) ethanamine(Ia); b. N-((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)-N-ethylethanamine (Ib); c. (((3-(phenylsulfonyl)-3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)azanediyl) dimethanol (Ic); d. (((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)azanediyl)dimethanol (Id); e. N-methyl-N-((3-(phenylsulfonyl)-3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)aniline (Ie); f. N-((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)-N-methyl aniline (If); g. 4-((3 -(phenylsulfonyl)-3H-Pyrrolo[2,3 -c]quinolin-4-yl)methyl)morpholine (Ig); h. 4-((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)morpholine (Ih); i. N,N-bis((3-(phenylsulfonyl)-3H-pyrrolo [2,3-c] quinolin-4-yl)methyl)aniline (Ii); j. N,N-bis((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)aniline (Ij); k. 4-methoxy-N-methyl-N-((3-(phenylsulfonyl)-3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)aniline (Ik); l. N-((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)-4-methoxy-N-methylaniline (Il) or m. N⁴-((3H-pyrrolo[2,3-c]quinolin-4-yl)methyl)-N¹,N¹-diethyl-N⁴-methylpentane-1,4-diamine (Im). n. 4-methyl-1H-pyrrolo[3,2-c]quinolone (In).
 3. A process for the preparation of compound of Formula I, dimers or pharmaceutically acceptable salt thereof as claimed in claim 1 and the said process comprising the steps of: i) charging [4-(bromomethyl)-3-(phenylsulfonyl)-3H-pyrrolo [2,3-c]quinoline of formula 1 and aliphatic amine in a solvent to obtain a reaction mixture; ii) refluxing the reaction mixture as obtained in step (i) at a temperature in the range of 70-90° C. for period in the range of 10-14 hr to obtain a solution; iii) charging [4-(bromomethyl)-3-(phenylsulfonyl)-3H-pyrrolo [2,3-c]quinoline of formula 1, base and aromatic amine in a solvent to obtain a reaction mixture; iv) refluxing the reaction mixture as obtained in step (iii) at a temperature in the range of 70-90° C. for period in the range of 10-14 hr followed by cooling and diluting with water and extracting the reaction mass into solvent; v) removing the solvent from the solution as obtained in step (ii) and (iv) under reduced pressure followed by purifying the crud product with flash silica gel column chromatography using an eluent to afford compound of formula I having —SO₂Ph as R₃. vi) charging the compound of formula I having —SO₂Ph as R₃ as obtained in step (v) and base in a solvent to obtain a reaction mixture; vii) refluxing the reaction mixture as obtained in step (vi) at a temperature in the range of 70-90° C. followed by removing the solvent under reduced pressure and dissolving the obtained residue in water and solvent; viii) extracting aqueous layer with solvent followed by washing the combined organic layer with brine and drying over sodium sulfate; ix) removing the solvent and purifying to obtain compound of formula I having —H as R₃.
 4. The process as claimed in claim 3, wherein said aliphatic amine is selected from the group comprising of diethylamine (HNEt₂), diethanolamine [HN(CH₂CH₂OH)_(2]) or N¹,N¹-diethylpentane-1,4-diamine.
 5. The process as claimed in claim 3, wherein said aromatic amine is selected from the group comprising of


6. The process as claimed in claim 3, wherein said solvent is selected from the group comprising of polar solvents, non-polar solvents, alcohol solvents, ether solvents, ester solvents, and the mixtures thereof.
 7. The process as claimed in claim 6, wherein polar solvents is selected from the group comprising of water, ammonia, sulfuric acid, deuterium oxide, ethanol, methanol, acetone, isopropanol, methyl ethyl ketone, n-propanol, acetonitrile, DMSO, DMF and mixtures thereof
 8. The process as claimed in claim 6, wherein nonpolar solvents is selected from the group comprising of chloroform, pentane, hexane, benzene, toluene, octane, decane, dimethyl ether, and dichloromethane, and mixtures thereof.
 9. The process as claimed in claim 6, wherein alcohol solvents is selected from the group comprising of methanol, ethanol, isopropanol, and mixtures thereof.
 10. The process as claimed in claim 6, wherein Ether solvents is selected from the group comprising of tetrahydrofuran, diethyl ether, 1,4-dioxane, methyl tert-butyl ether, and mixtures thereof and Ester solvents is selected from the group comprising of methyl acetate, ethyl acetate, isopropyl acetate, tert-butyl acetate, and mixtures thereof.
 11. The process as claimed in claim 3, wherein said base is selected from the group comprising of sodium hydroxide, potassium hydroxide, sodium carbonate (Na₂CO₃) or potassium carbonate (K₂CO₃), sodium bicarbonate (NaHCO₃), potassium bicarbonate (KHCO₃).
 12. The process for the preparation of heterocyclic compound, N⁴-((3H-pyrrolo [2,3-c]quinolin-4-yl)methyl)-N¹,N¹-diethyl-N⁴-methylpentane-1,4-diamine, of Formula (Im) as claimed in claim 2, wherein said process comprises of: A) heating the reaction mixture of 4-methyl-3-(phenylsulfonyl)-3H-pyrrolo[2,3-c] quinoline of formula 2 and selenium dioxide (SeO₂) in a solvent at a temperature in the range of 60° C. to 80° C. for the period in the range of 10 to 14 hrs to afford 3-(phenylsulfonyl)-3H-Pyrrolo[2,3-c]quinoline-4-carbaldehyde of formula 3;

B) stirring the reaction mixture of step (a) and N¹,N¹-diethylpentane-1,4-diamine in presence of 4A molecular sieves in a solvent at temperature in the range of 25 to 30° C. for the period in the range of 20 to 24 hrs to afford crude imine of formula 4;

C) adding sodium borohydride to a cooled solution of crude imine of step (b) in a solvent followed by refluxing the reaction mixture at temperature in the range of 60 to 80° C. for the period in the range of 10 to 20 minutes to afford crude amine of formula 5;

D) refluxing the reaction mixture of crude amine of step (c) in solvent and formaldehyde at temperature in the range of 60 to 80 ° C. for the period in the range of 20 minutes to 30 min followed by cooling reaction mixture at 0° C. and adding sodium borohydride (NaBH₄) at 0° C. and stirring the reaction mixture at a temperature in the range of 25 to 30 ° C. for the period in the range of 20 to 24 h to afford heterocyclic compound of formula (Im).


13. A pharmaceutical composition comprising a heterocyclic compound of Formula I, dimers, or pharmaceutically acceptable salt thereof, and a pharmaceutically acceptable carrier, diluent or excipient.
 14. The pharmaceutical composition as claimed in claim 13, wherein said composition is useful as an antimalarial.
 15. A method for the treating or preventing malarial infection in a subject in need thereof comprising administering a therapeutically effective amount of a compound formula I dimers, or pharmaceutically acceptable salt thereof. 